Epoxy resin adhesives possess excellent adhesion and bonding properties to materials, for example, metals, plastics, glasses, ceramics, etc. Due to the excellent performance in mechanical property, electrical insulation, heat resistance, and chemical resistance of the cured bonding products, epoxy resin adhesives have been widely applied in machinery manufacturing, electrical and electronics, aerospace, shipbuilding, automotive, construction and others.
Such an adhesive is expected to have a suitable viscosity, especially not to be very viscous, in order to be applied and spread on the substrate evenly in a short period of time. This may increase the efficiency of an assembly process in automated manufacturing. The bonding strength of such an adhesive depends on the compatibility between adhesive and the substrate to which, the adhesive is to be applied, i.e., on the adhesion between adhesive and substrate. However, the bonding strength also relies on the cohesion of the adhesive itself. Even small changes in the composition of the adhesive, for example, some additives including diluent or in its molecular structure may give rise to a drastic reduction in bond strength. And therefore, it may make the adhesive completely unusable or may weaken, or even totally destroy a bond produced by using such an adhesive.
CN102911631 discloses a one-part epoxy resin adhesive composition, comprising at least one non-toughed epoxy resin; a toughed epoxy resin; a polyether amine modified epoxy prepolymer, an aging additive containing carbodiimide; a latent curing agent. In order to lower the viscosity of the product, monofunctional epoxy reactive diluent is further added. Although the adhesive product exhibits a good stability even after aging, the initial and post-aging lap shear strength are both lower than 35 MPa.
Accordingly, there is still a need for a one-part curable epoxy resin adhesive composition having a lower viscosity, an excellent aging behavior and providing a better adhesive strength.